Process Color Printing On A One-color Press

Getting back to sequence, to prevent any possible back trap contamination problems, on the first pass print the yellow on the first unit followed by black on the second unit. If there is any back trap contamination because of ink film thickness due to plate coverage or incorrect ink tacks, the yellow will back trap into the black and be unnoticed. You don't want the reverse, which is your yellow ink becoming dirty because it is being back trap contaminated with black.